It's always a good idea to clean a new gun, although I admit that I don't always do it either. There might be bits of grit and metal left inside from the manufacturing process plus most of them do use a fairly heavy grease/oil because they have no idea how long the product might sit in a warehouse or a dealers shelf before being sold.
Wait 'till you buy a milsurp. They could mold a statue out of that cosmoline they pack those things in.
After reading all these posts lately about the MK III, I decided I needed another one myself.